It happens all the time. Friends turn to more than friends turn to couples, but what's this? The girl in his social group that he got with that time at pres in the smoking area of the club? That guy 'pal' she was caught crushing on the whole of uni before you came along?
They're still mates with them even after all this time, and that's got you majorly paranoid, but why though?
Should you even give a single fuck about their past?
No you fucking shouldn't.
Yes they have a past, yes it sticks around like a little notification update, but it's not there to THREATEN YOU.
At the end of the day, they picked you, they went through all those grimy chat up lines, tinder dates and one night regrets, they fancied a few, maybe even declared undying love to a handful of the exes, but the point is they went through them and chose YOU in the end.. YOU got the golden buzzer, YOU get taken home to be boned each night.
Do you know what the best bit is? You're better than everyone they've ever been with before, not because those people are bad people, everyone's a good person for someone else, but they weren't their person, you're THEIR person, you're the newest update, the one with the new features they didn't know they needed until now. So why are you worried?!
Embrace their ex crushes, their ex bangs, their ex undying lovers. People get crushes, but relationships are real, and you reached the real, and that's all that matters.